David Letterman retirement: Obama, Ellen, Kimmel react on Twitter

David Letterman sits at his "Late Show" desk during the broadcast in which he announced his retirement.

David Letterman sits at his "Late Show" desk during the broadcast in which he announced his retirement. (Jeffrey R. Staab / CBS / Associated Press)

Meredith Blake

After David Letterman announced Thursday that he would be retiring after more than three decades in late-night television, the news, though not exactly unexpected, sparked an immediate response on Twitter.

With the genre's elder statesman planning to sign off in 2015, celebrities of all stripes weighed in on the latest upheaval in late night.